Dimerization of CO2 at high pressure and temperature

Two's company: Constant-pressure ab initio molecular dynamics simulations reveal the reaction of two CO2 molecules to form the metastable C2O4 species (see picture) in high-temperature (4000 K) and high-pressure (≥ 20 GPa) liquid CO2. The dimer exhibits a unique Raman-active vibrational mode, which is characteristic for this molecule and consistent with experimental observations.